This all really depends on what you did before, which is not quite clear from your description. Picard does not explicitly make a request to AcoustID to check whether it already exist. But e.g. if you used “Scan” and Picard found matches and moved the files to the matched tracks on the right it will not enable submission. That’s because obviously AcoustID already knows about this match between fingerprint and MB recording ID, otherwise it would not had any results to begin with. But if you use “Generate fingerprints” on already matched files on the right (which where not matched using Scan) it will just generate the fingerprint and allow you to submit it. I recently explained this in more detail at
Please also see also the docs at Understanding Acoustic Fingerprinting and AcoustIDs — MusicBrainz Picard v2.10 documentation
It’s also important to understand that a AcoustID and the AcoustID acoustic fingerprint are not the same. The presence of the AcoustID is not sufficient to submit anything, you need to generate the actual acoustic fingerprint (using “Scan” and/or “Generate fingerprints”). Likewise generating the fingerprint does not mean you will have a AcoustID tag. I.e. “Generate fingerprints” does not do any request against the AcoustID server and only generates the fingerprint (for later submission). “Scan” does query the AcoustID server for matching AcoustIDs, but it might not get a result.